JP6130845B2 - Separator integrated electrode and non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a separator integrated electrode and a nonaqueous electrolyte secondary battery including the separator integrated electrode.

  In recent years, mobile information terminals such as mobile phones and notebook personal computers have been rapidly reduced in size and weight, and a battery as a driving power source is required to have a higher capacity. Among secondary batteries, the capacity of non-aqueous electrolyte secondary batteries represented by lithium (Li) ion batteries having a high energy density is increasing year by year, but at present, the demand is not fully met. Recently, using the characteristics of nonaqueous electrolyte secondary batteries, not only mobile applications such as mobile phones, portable computers, PDAs, and portable music players, but also electric tools, electric bicycles, electric vehicles (EV), Development is progressing for medium-sized to large-sized battery applications ranging from power for hybrid electric vehicles (HEV, PHEV) to power storage such as backup power supplies and power storage, and the applications are diversifying.

  The structure of the nonaqueous electrolyte secondary battery has also diversified according to the use of these nonaqueous electrolyte secondary batteries, and a cylindrical battery using a wound electrode body in which an electrode and a separator are wound in a spiral shape, A rectangular battery in which the wound electrode body is press-molded and inserted into a rectangular outer can or covered with a laminated outer casing, and an electrode body in which an electrode and a separator are laminated is inserted into a rectangular outer can or covered with a laminated outer casing, Button-type batteries have been developed.

  The manufacturing process of non-aqueous electrolyte secondary batteries has become more complex due to the diversification of non-aqueous electrolyte secondary battery shapes. This has led to increased production costs and lead times for non-aqueous electrolyte secondary batteries. Sexual deterioration will occur. For this reason, in the manufacture of diversifying non-aqueous electrolyte secondary batteries, it is essential to develop a technology that simplifies the manufacturing process of non-aqueous electrolyte secondary batteries.

  Polyolefin microporous membranes used as separators for non-aqueous electrolyte secondary batteries increase the material cost of the battery, and the winding and lamination process with the electrodes complicates the manufacturing process and increases the lead time. Invite. For this reason, the present inventors have made various attempts to develop a separatorless battery without using a conventional polyolefin microporous membrane.

  In a conventional nonaqueous electrolyte secondary battery, an insulating porous material that transmits lithium ions is used as a separator between a positive electrode plate and a negative electrode plate. This separator is made of polyolefin, for example, made of polyethylene or polypropylene. A microporous membrane is used. In order to obtain a separatorless battery that does not include this separator in a non-aqueous electrolyte secondary battery, it is necessary to directly form a porous layer made of a low-cost material instead of a polyolefin microporous film on the electrode surface. .

  In the following Patent Document 1, a negative electrode formed by laminating a negative electrode active material coating layer on a current collector, a positive electrode formed by laminating a positive electrode active material coating layer on a current collector, a separator, and a non-aqueous electrolyte A non-aqueous electrolyte secondary battery having a negative electrode active material coating layer or a positive electrode active material coating layer having a resin binder and alumina powder or silica powder having a particle size in the range of 0.1 to 50 μm on the surface An invention of a non-aqueous electrolyte secondary battery in which a porous protective film containing solid fine particles is formed to have a thickness in the range of 0.1 to 200 μm is disclosed. In the following Patent Document 2, an electrochemical device formed by a porous layer containing a fiber formed by an electrospinning method as a separator in a separator electrode integrated power storage device for an electrochemical device in which a separator is joined and integrated with an electrode surface. An invention of an element separator integrated power storage element is disclosed.

Japanese Patent No. 3371301 JP 2010-225809 A

  According to the invention disclosed in Patent Document 1, a non-aqueous electrolyte in which an internal short circuit due to a falling active material is suppressed by a porous protective film formed on the surface of a negative electrode active material coating layer or a positive electrode active material coating layer. A secondary battery can be obtained. Further, according to the invention disclosed in Patent Document 2, a porous layer containing fibers is formed on the surface of the active material mixture layer of the electrode, so that the porous layer is thinned without impairing mechanical strength. An electrochemical element separator-integrated energy storage device that can be layered and can reduce internal resistance can be obtained.

  However, according to the experiment results of the present inventors, a porous layer made of solid particles or a porous layer containing fibers having a diameter of less than 1 μm was formed on the surface of the negative electrode active material mixture layer or the positive electrode active material mixture layer. It was found that when a separatorless non-aqueous electrolyte secondary battery was fabricated using an electrode, dendritic lithium metal was deposited on the surface of the active material mixture layer during the initial charge, causing an internal short circuit. .

  This is because, when a porous layer made of solid particles or a porous layer containing fibers having a diameter of less than 1 μm is used, when a thin layer of several tens of μm is formed, the micro shape tends to be non-uniform, and the lithium ion This means that the distribution of the low resistance portion with respect to transmission occurs. As a result, the lithium ion concentration in the low resistance portion with respect to the permeation of lithium ions increases during the initial charge, and dendritic lithium metal precipitates on the surface of the active material mixture layer, so that the physical properties between the positive electrode and the negative electrode can be reduced. A short circuit will occur.

  According to the present invention, a separator having a porous layer on the surface of a positive electrode mixture layer or a negative electrode mixture layer, in which the deposition of lithium metal is suppressed and the occurrence of a short circuit between the positive electrode and the negative electrode can be suppressed. An integrated electrode and a nonaqueous electrolyte secondary battery using the separator integrated electrode can be provided.

  The separator-integrated electrode of the present invention includes a current collector, an electrode mixture layer formed on the current collector, and a porous layer formed on the electrode mixture layer. The quality layer includes particles made of an inorganic material and fibers made of a resin material.

  In the separator-integrated electrode of the present invention, since the porous layer formed on the surface of the electrode mixture layer is formed of particles including inorganic material particles and resin material fibers, As a result, it becomes difficult to make the fine shape of the porous layer non-uniform as in the technology, and the generation of a low resistance portion against the permeation of lithium ions is suppressed. Thereby, according to the separator integrated electrode of this invention, precipitation of the dendritic lithium metal resulting from an increase in lithium ion concentration in a low resistance part is suppressed. Therefore, when a non-aqueous electrolyte secondary battery is formed using the separator-integrated electrode of the present invention, the occurrence of a short circuit between the electrodes is suppressed, and a non-aqueous electrolyte secondary battery with improved reliability and electrochemical characteristics is obtained. It becomes like this.

  The fiber made of a resin material forming the separator-integrated electrode of the present invention is preferably a fibrous resin material having a diameter of 1 to several 100 nm, but a fiber of about several μm can also be used. The separator-integrated electrode of the present invention is applied to the positive electrode in which the positive electrode active material mixture layer is formed on the surface of the positive electrode current collector and the negative electrode in which the negative electrode active material mixture layer is formed on the surface of the negative electrode current collector. However, the same can be applied.

  In the separator-integrated electrode according to this aspect, the porous layer includes a first porous layer including particles made of an inorganic material formed on the electrode mixture layer, and the first porous layer. And a second porous layer containing fibers made of a resin material formed thereon.

  With such a configuration, a first porous layer containing inorganic material particles and a second porous layer formed of resin material fibers are formed on the surface of the electrode mixture layer. Therefore, the characteristics based on the difference in the forming material of each porous layer are favorably exhibited.

  In the separator-integrated electrode according to such an embodiment, when the average thickness of the second porous layer is x and the average thickness of the first porous layer is y, 0.5 ≦ x / (x + y) ≦ 0.95 It is preferable to do.

  X / (x + y) obtained by dividing the thickness x of the porous layer constituted by the fiber made of the resin material by the total thickness (x + y) of the porous layer containing the particles made of the inorganic material and the fiber made of the fiber. If the value of) is less than 0.5, the resistance distribution between the porous layer containing particles made of inorganic material and the porous layer formed of fibers becomes non-uniform, and an internal short circuit is likely to occur. When the value of x / (x + y) exceeds 0.95, the generation of the low resistance portion with respect to the permeation of lithium ions in the porous layer constituted by the fiber made of the resin material is further suppressed, but the internal resistance increases. Therefore, it is not preferable.

  In the separator-integrated electrode according to this aspect, the fiber made of a resin material forming the second porous layer is made of polypropylene, polyethylene, polystyrene, polyethylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m. -Phenylene terephthalate, poly-p-phenylene isophthalate, polyvinylidene fluoride, polytetrafluoroethylene, poly (vinylidene fluoride-tetrafluoroethylene) copolymer, poly (vinylidene fluoride-hexafluoropropylene) copolymer, poly (Vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene) copolymer, poly (tetrafluoroethylene-hexafluoropropylene) copolymer, polyvinyl chloride, polyvinyl chloride -Acrylate copolymer, polyacrylonitrile, polyacrylonitrile-methacrylate copolymer, polycarbonate, polyarylate, polyester carbonate, polyamide, aramid, polyimide, polycaprolactone, polylactic acid, polyvinyl alcohol, polyglycolic acid, collagen, polyhydroxybutyric acid It is preferably composed of at least one selected from the group consisting of polyvinyl acetate, polypeptide, and a high molecular weight material of these copolymers.

  Since the second porous layer produced using these resin-made fibers can be obtained with good electrical insulation and porosity, when a non-aqueous electrolyte secondary battery is formed, This makes it possible to obtain a non-aqueous electrolyte secondary battery in which lithium dendrite is less likely to occur and internal short circuit is less likely to occur.

  In the separator-integrated electrode of this aspect, the inorganic material particles contained in the first porous layer are at least one selected from titania (excluding anatase structure), alumina, zirconia, and magnesia. Preferably there is.

  These inorganic material particles have good electrical insulation, low cohesiveness, and good dispersibility in a solvent, so that a homogeneous first porous layer can be easily formed. Will be able to.

  In the separator-integrated electrode of this aspect, it is preferable that the fiber of the resin material forming the second porous layer is formed by an electrospinning method.

  According to the electrospinning method, compared to other methods, the shape of the formed fiber can be easily controlled, the fiber length can be easily increased, and the resin material that can be used is less limited. In addition, since the fiber can easily enter the pores of the insulating first porous layer by electrostatic force, the second porous layer can be formed more stably and the second porous layer can be formed. The adhesion strength between the layer and the first porous layer is increased.

  A non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery comprising any of the above-described separator integrated electrode and a counter electrode paired with the separator integrated electrode, The counter electrode has a counter electrode mixture layer formed on the surface of the current collector, and the counter electrode mixture layer is disposed so as to be in contact with the second porous layer of the separator-integrated electrode, The first porous layer and the second porous layer of the separator-integrated electrode are impregnated with a nonaqueous electrolytic solution. The nonaqueous electrolyte secondary battery may include a separate separator.

  According to the nonaqueous electrolyte secondary battery of the present invention, the occurrence of a short circuit between the electrodes is suppressed, and a highly reliable nonaqueous electrolyte secondary battery is obtained.

FIG. 1 is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment. FIG. 2 is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery according to a modification.

  A mode for carrying out the present invention will be described in detail. However, the embodiment described below is illustrated for understanding the technical idea of one aspect of the present invention, and is not intended to specify the present invention as the embodiment. The present invention can be equally applied to various modifications without departing from the technical idea shown in the claims. Since the separator-integrated electrode according to the present invention can be applied to both the positive electrode and the negative electrode, the following description will be made taking the positive electrode as a representative.

  A nonaqueous electrolyte secondary battery 10 according to an embodiment will be described with reference to FIG. In the nonaqueous electrolyte secondary battery 10 according to the embodiment, the positive electrode 12 is a separator-integrated electrode, and the positive electrode 12 and the negative electrode 14 that are the separator-integrated electrode are stacked.

  In the positive electrode 12, a positive electrode current collector 22, a positive electrode mixture layer 24, a first porous layer 26 including particles made of an inorganic material, and a second porous layer 28 including a resin material are laminated. It has a configuration. The negative electrode 14 has a configuration in which a negative electrode current collector 32 and a negative electrode mixture layer 34 are laminated.

  Specifically, the positive electrode 12 includes a positive electrode current collector 22 made of aluminum or an aluminum alloy, a positive electrode mixture layer 24 formed on the surface of the positive electrode current collector 22, and a positive electrode current collector of the positive electrode mixture layer 24. The first porous layer 26 formed on the surface opposite to the electric body 22 and the second porous layer formed on the surface opposite to the positive electrode mixture layer 24 of the first porous layer 26. And a quality layer 28.

Examples of the positive electrode active material capable of occluding and releasing lithium ions contained in the positive electrode mixture layer 24 include lithium cobalt composite oxide (LiCoO ₂ ), lithium manganese composite oxide (LiMn ₂ O ₄ , LiMnO ₂ ), lithium nickel composite oxide (LiNiO _2), lithium nickel cobalt composite oxide _{(LiNi x Co 1-x O} 2 (x = 0.01~0.99)), lithium nickel manganese cobalt composite oxide (LiNi _x Mn _y Co _z O ₂ (x + y + z = 1)) or lithium ferrate (LiFePO ₄ ) is used singly or in combination. What added different metal elements, such as zirconium, magnesium, and aluminum, to lithium cobalt complex oxide can also be used.

The first porous layer 26 is composed of, for example, particles made of an inorganic material and a resin material. As the particles made of an inorganic material, titania (TiO ₂ ), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), magnesia (MgO), or the like can be used. As compared with the anatase structure, the rutile-structure titania is less prone to the desorption / insertion of lithium ions, and is less likely to cause occlusion of lithium ions or expression of electronic conductivity due to the environmental atmosphere (potential). For this reason, since the fall of a capacity | capacitance and generation | occurrence | production of a short circuit are suppressed more, it is preferable that a titania is a rutile structure. In addition, these particles made of an inorganic material preferably have an average particle size of 1 μm or less, and are surface-treated with aluminum (Al), silicon (Si), titanium (Ti) or the like in consideration of the dispersibility of the slurry. Those are particularly preferred.

  As the resin material constituting the first porous layer 26, a water-insoluble resin or a water-soluble resin can be used. As the water-insoluble resin, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyamide, polyamideimide, polytetrafluoroethylene and the like can be used. As the water-soluble resin, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyvinyl methyl ether, polyethylene glycol, or the like can be used.

  The resin-based material constituting the first porous layer 26 is preferably dissolved in a solvent different from the solvent used for the positive electrode mixture slurry for forming the positive electrode mixture layer. Therefore, when the positive electrode active material mixture layer is formed with the positive electrode mixture slurry using N-methyl-2-pyrrolidone (NMP) as the solvent and the first porous layer 26 is formed on this surface, the first porous layer is formed. The solvent that dissolves the resin-based material constituting the porous layer 26 is preferably water.

  In order to form the first porous layer 26, the inorganic material particles are dispersed, and the solvent for dissolving the resin material is N, N-dimethylacetamide (DMAc), N- Examples thereof include methyl-2-pyrrolidone (NMP), phosphoric acid hexamethyltriamide (HMPA), N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and γ-butyrolactone. The solvent for dispersing these inorganic material particles and dissolving the resin-based material may be appropriately selected according to the solubility of the resin-based material, and is not limited to these.

  As a method of forming the first porous layer 26 on the surface of the positive electrode mixture layer 24, a slurry in which inorganic material particles and resin material are dispersed and dissolved in a solvent is formed on the surface of the positive electrode mixture 24. A coating method, a gravure coating method, a spray coating method, a die coating method, a roll coating method, a dip coating method, a screen printing method, or the like can be used.

  The second porous layer 28 is composed of fibers. The resin material constituting the fiber is polypropylene, polyethylene, polystyrene, polyethylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, polyvinylidene fluoride, poly Tetrafluoroethylene, poly (vinylidene fluoride-tetrafluoroethylene) copolymer, poly (vinylidene fluoride-hexafluoropropylene) copolymer, poly (vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene) copolymer, Poly (tetrafluoroethylene-hexafluoropropylene) copolymer, polyvinyl chloride, polyvinylidene chloride-acrylate copolymer, polyacrylonitrile, polyacrylate Lilonitrile-methacrylate copolymer, polycarbonate, polyarylate, polyester carbonate, polyamide, aramid, polyimide, polycaprolactone, polylactic acid, polyvinyl alcohol, polyglycolic acid, collagen, polyhydroxybutyric acid, polyvinyl acetate, polypeptide, and the like A high molecular weight material such as a copolymer can be used. Moreover, the kind chosen from the above may be sufficient and multiple types may be mixed. In addition, said resin material is an illustration and it is not limited to these as resin material which comprises a fiber.

  As a method for forming the second porous layer 28 formed of fibers on the surface of the first porous layer 26, a known electrospinning method, self-assembly method, phase separation method, or the like can be used. . From the viewpoint of productivity and stability, the electrospinning method is preferable. In the electrospinning method, a high voltage is applied between the spinning solution contained in the container and the collector electrode on the object side, so that the spinning solution is pushed out of the container and attached to the object as finely charged fibers. It is a method to make it. Here, the second porous layer 28 may be formed on the surface of the first porous layer 26 using the positive electrode current collector 22 as a collector electrode.

  In forming the second porous layer 28 by electrospinning, first, a spinning solution is prepared by mixing and dispersing a resin material in a solvent. A method for mixing and dispersing the resin material in the solvent is not particularly limited, and a planetary mixer, a homomixer, a pin mixer, a kneader, a homogenizer, or the like can be used. When mixing and dispersing the resin material in the solvent, various inorganic particles, a dispersant, a surfactant, a stabilizer, a crosslinking agent, and the like may be added as necessary.

  The spinning solution is supplied to the nozzle, pushed out from the nozzle, and an electric field is applied to the extruded spinning solution, so that an electrostatic charge is accumulated in the spinning solution and is electrically pulled and stretched by the collector-side electrode. Fiberized. In the electrospinning method, the fibers formed by extrusion are electrically stretched, so that the velocity is accelerated by the electric field as the position approaches the collector, and the fibers have a smaller fiber diameter. In the meantime, it becomes thinner by evaporation of the solvent, the electrostatic density is increased, it is split by the electric repulsive force, and it becomes a fiber having a smaller fiber diameter. Although the voltage applied in order to make this electric field act is not specifically limited, It is preferable to set it as about 5-50 kV. The polarity of the applied voltage may be either positive or negative. Further, the formed fiber layer may be pressed in order to adjust the porosity of the formed fiber layer.

  Solvents used in the spinning solution include methanol, ethanol, 1-propanol, 2-propanol, hexafluoroisopropanol, tetraethylene glycol, triethylene glycol, dibenzyl alcohol, 1,3-dioxolane, 1,4-dioxane, methyl ethyl ketone. , Methyl isobutyl ketone, methyl-n-hexyl ketone, methyl-n-propyl ketone, diisopropyl ketone, diisobutyl ketone, acetone, hexafluoroacetone, phenol, formic acid, methyl formate, ethyl formate, propyl formate, methyl benzoate, benzoic acid Ethyl, propyl benzoate, methyl acetate, ethyl acetate, propyl acetate, dimethyl phthalate, diethyl phthalate, dipropyl phthalate, methyl chloride, ethyl chloride, methylene chloride, chloroform o-chlorotoluene, p-chlorotoluene, chloroform, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, trichloroethane, dichloropropane, dibromoethane, dibromopropane, methyl bromide, ethyl bromide, propyl bromide , Acetic acid, benzene, toluene, hexane, cyclohexane, cyclohexanone, cyclopentane, o-xylene, p-xylene, m-xylene, acetonitrile, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, Pyridine, water, etc. can be used. One kind selected from the above may be used, or a plurality of kinds may be mixed. In addition, the solvent used for these spinning solutions is an illustration, and is not limited to these.

  As the inorganic material added to the spinning solution, oxides, carbides, nitrides, borides, silicides, fluorides, sulfides, and the like can be used. From the viewpoints of heat resistance and processability of the manufactured fiber, it is preferable to use an oxide as the inorganic material added to the spinning solution.

Examples of the oxide added to the spinning solution include Al ₂ O ₃ , SiO ₂ , TiO ₂ , Li ₂ O, Na ₂ O, MgO, CaO, SrO, BaO, B ₂ O ₃ , P ₂ O ₅ , SnO _{2. , ZrO 2, K 2 O,} Cs 2 O, ZnO, Sb 2 O 3, As 2 O 3, CeO 2, V 2 O 5, Cr 2 O 3, MnO, Fe 2 O 3, CoO, NiO, Y 2 O ₃ , Lu ₂ O ₃ , Yb ₂ O ₃ , HfO ₂ , Nb ₂ O _{5 and the} like can be used. One kind selected from the above may be used, and a plurality of kinds may be mixed. The oxides added to these spinning solutions are examples and are not limited thereto.

  The mixing ratio of the solvent and the solute in the spinning solution varies depending on the type of solvent selected and the type of solute, but the solvent amount is preferably about 60% by mass to 98% by mass, and the solute is 2 to 40% by mass. % Is preferable.

The negative electrode 14 has a configuration in which a negative electrode current collector 32 made of copper or a copper alloy and a negative electrode mixture layer 34 are laminated. Examples of the negative electrode active material capable of occluding and releasing lithium ions contained in the negative electrode mixture layer 34 include carbon raw materials such as graphite, non-graphitizable carbon and graphitizable carbon, LiTiO ₂ and TiO ₂ . Titanium oxide, metalloid elements such as silicon and tin, silicon oxide (SiOx, 0.5 ≦ x <1.6), Sn—Co alloy, or the like may be used.

The production of the nonaqueous electrolyte secondary battery according to Example 1 will be described.
[Production of separator integrated electrode]
The separator integrated electrode was produced as follows.
(Formation of positive electrode mixture layer)
The mass ratio of lithium cobaltate (LiCoO ₂ ) as the positive electrode active material, acetylene black as the conductive material, and polyvinylidene fluoride (PVdF) as the binder is 95: 2.5: 2.5, respectively. The mixture was weighed and mixed with N-methyl 2-pyrrolidone (NMP) as a dispersion medium to prepare a positive electrode mixture slurry. Then, this positive electrode mixture slurry is applied to the surface of an aluminum foil as a positive electrode conductor by a die coater, then dried to remove NMP as an organic solvent, and compressed to a predetermined thickness by a roll press, A positive electrode was obtained by cutting into a predetermined size.

(Formation of the first porous layer)
Titanium oxide (manufactured by Nippon Titanium Industry Co., Ltd .: KR-380) as an inorganic material particle and acrylic resin were weighed to be 3.75: 96.25, respectively, and the solid content concentration was 30% by mass. The mixture was mixed with water as a dispersion medium. This mixture was mixed and dispersed with a fill mix (manufactured by Filmix Co., Ltd., manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a titanium oxide dispersion slurry. Then, this titanium oxide dispersion slurry was applied to the surface of the positive electrode mixture layer by a gravure coating method, and the dispersing agent was dried and removed to form a first porous layer having a thickness of 8 μm.

(Formation of second porous layer)
A polyvinyl alcohol resin (PVA) was mixed with water so as to be 10% by mass, and this was mixed and dispersed with TK Robotics (Tajima Chemical Machinery Co., Ltd.) to prepare a spinning solution. The spinning solution was spun using an electrospinning method under an applied voltage of 30 kV, and then pressed to form a second porous layer having a basis weight of 10 g / m ² and a thickness of 23 μm. This produced the separator integrated electrode of the embodiment.

[Production of negative electrode]
The negative electrode was prepared as follows.
Carbon material (graphite) as a negative electrode active material, sodium carboxymethylcellulose (CMC) as a thickener, and styrene butadiene rubber (SBR) as a binder are each in a mass ratio of 98: 1: 1. And were dispersed in water to prepare a negative electrode mixture slurry. This negative electrode mixture slurry is applied to the surface of a copper foil as a negative electrode current collector by a die coater, dried to form a negative electrode active material mixture layer on both sides of the negative electrode current collector, and then using a compression roller It was compressed to a predetermined thickness and cut into a predetermined size to obtain a negative electrode.

[Preparation of non-aqueous electrolyte]
The nonaqueous electrolytic solution was prepared as follows. Lithium hexafluorophosphate (LiPF ₆₎ as an electrolyte salt was added to a non-aqueous solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio (1 atm, 25 ° C.) in a ratio of 3: 7. ) Was dissolved at a rate of 1.0 mol / L.

[Assembly of non-aqueous electrolyte secondary battery]
A non-aqueous electrolyte secondary battery, which is a separatorless battery, was produced as follows. An electrode body obtained by attaching and laminating lead terminals (not shown) to each of the separator-integrated electrode and the negative electrode is inserted into an aluminum laminate battery exterior body, and a nonaqueous electrolyte is injected into the battery exterior body and sealed. .

  The nonaqueous electrolyte secondary battery according to Example 2 was different from the separator integrated electrode except that the first porous layer was formed to have a thickness of 13 μm and the second porous layer had a thickness of 17 μm. This was produced in the same manner as in Example 1.

[Comparative Example 1]
The nonaqueous electrolyte secondary battery according to Comparative Example 1 was the same as that of the separator integrated electrode except that the first porous layer was not formed and the second porous layer was formed to a thickness of 24 μm. This was produced in the same manner as in Example 1.

[Comparative Example 2]
In the nonaqueous electrolyte secondary battery according to Comparative Example 2, in the production of the separator-integrated electrode, the first porous layer was formed to have a thickness of 30 μm, and the second porous layer was not formed. Except for the above, it was produced in the same manner as in Example 1.

[Internal short circuit test]
An internal short circuit test was performed on each of the nonaqueous electrolyte secondary batteries according to Examples 1 and 2 and Comparative Examples 1 and 2 manufactured as described above. The outline of the internal short circuit test is as follows.

  For each of the nonaqueous electrolyte secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 2, the charging behavior was observed when the battery voltage was charged to a voltage of 4.4 V at a constant current value of 0.2 It. If the battery voltage does not reach 4.4V when the battery is charged up to 4.4V, if the battery voltage does not reach 4.4V, an internal short circuit has occurred, and the battery voltage reaches 4.4V. In the case where there was an internal short circuit, it was determined whether or not an internal short circuit occurred. This is based on the fact that when an internal short circuit occurs in a non-aqueous electrolyte secondary battery, a minute short circuit current flows between the positive electrode and the negative electrode, so that the battery voltage does not rise normally even when charged to the design capacity. Is.

  The results of the internal short circuit test of each of the nonaqueous electrolyte secondary batteries according to Examples 1 and 2 and Comparative Examples 1 and 2 are shown as follows: thickness y of the first porous layer, thickness x and x of the second porous layer The values are shown together with the value of / (x + y) in Table 1.

  From the results shown in Table 1, the following can be understood. That is, in Examples 1 and 2 in which both the first porous layer and the second porous layer were formed, an internal short circuit did not occur. In contrast, in Comparative Examples 1 and 2 in which either the first porous layer or the second porous layer was not formed, an internal short circuit occurred.

  Further, when the thickness of the first porous layer is y and the thickness of the second porous layer is x, the thickness of the second porous layer is set to the first porous layer and the second porous layer. When the value of x / (x + y) divided by the total thickness of the layer is 0.5 or more and 0.9 or less (that is, 0.5 ≦ x / (x + y) ≦ 0.95), and not in this range As compared with the above, the effect of suppressing the internal short circuit while exhibiting the penetration of the electrolyte into the electrode was exhibited more greatly.

  The positive electrode mixture layer 24 is formed on both surfaces of the positive electrode current collector 22, and the first porous layer 26 and the second porous layer 28 are respectively formed on the positive electrode mixture layer 24 formed on both surfaces. Alternatively, the negative electrode 14 may be disposed opposite to the both sides.

<Modification>
The nonaqueous electrolyte secondary battery 10 according to the embodiment is applied to the positive electrode as the separator-integrated electrode. However, an example in which the nonaqueous electrolyte secondary battery 10A according to the modification is applied to the negative electrode will be described with reference to FIG. To do. In FIG. 2, the same components as those of the nonaqueous electrolyte secondary battery 10 of the embodiment are given the same reference numerals, and detailed descriptions thereof are omitted.

  In the nonaqueous electrolyte secondary battery 10A of the modification, the negative electrode 42 is formed as a separator integrated electrode, and the negative electrode 42 and the positive electrode 44 that are separator integrated electrodes are stacked.

  In the negative electrode 42, a negative electrode current collector 32, a negative electrode mixture layer 34, a first porous layer 26 containing particles made of an inorganic material, and a second porous layer 28 containing a resin material are laminated. It has a configuration. The positive electrode 44 has a configuration in which the positive electrode current collector 32 and the positive electrode mixture layer 24 are laminated.

  The configurations of the negative electrode current collector 32 and the negative electrode mixture layer 34 of the negative electrode 42 can be the same as those in the nonaqueous electrolyte secondary battery 10 of the embodiment, and the positive electrode current collector 22 and the positive electrode mixture layer of the positive electrode 44. The configuration of 24 can be the same as that in the nonaqueous electrolyte secondary battery 10 of the embodiment.

  Moreover, the structure of the 1st porous layer 26 formed in the surface of the negative mix layer 34 of the negative electrode 42 is the same as the thing in the nonaqueous electrolyte secondary battery 10 of embodiment. Furthermore, the configuration of the second porous layer 28 formed on the surface of the first porous layer 26 of the negative electrode 42 is also the same as that in the nonaqueous electrolyte secondary battery 10 of the embodiment.

  However, since the negative electrode mixture layer 34 is produced using a negative electrode mixture slurry containing water as a solvent, the resin material constituting the first porous layer 26 should be an organic solvent material. Is preferred. The composition and formation method of the first porous layer 26 and the composition and formation method of the second porous layer 28 formed on the first porous layer 26 are also the same as those of the nonaqueous electrolyte secondary battery 10 of the embodiment. Can be the same as in Also in the nonaqueous electrolyte secondary battery 10A of the modified example having such a configuration, the same operational effects as those of the nonaqueous electrolyte secondary battery 10 of the embodiment are exhibited.

  In addition, in the nonaqueous electrolyte secondary battery 10A of the modified example, the negative electrode mixture layer 34 is formed on both surfaces of the negative electrode current collector 32, and the first negative electrode mixture layer 34 formed on both surfaces is the first. The porous layer 26 and the second porous layer 28 may be formed, and the positive electrodes 44 may be disposed opposite to each other.

DESCRIPTION OF SYMBOLS 10, 10A ... Electrode body 12 ... Separator integrated electrode 14 ... Negative electrode 18 ... 2nd porous layer 22 ... Positive electrode collector 24 ... Positive electrode mixture layer 26 ... 1st porous layer 28 ... 2nd porous Layer 32 ... Negative electrode current collector 34 ... Negative electrode mixture layer 40 ... Electrode body 42 ... Separator integrated electrode 44 ... Positive electrode

Claims (6)

A current collector, an electrode mixture layer formed on the current collector, and a porous layer formed on the electrode mixture layer;
The porous layer is formed on the electrode mixture layer, formed on the first porous layer, a first porous layer containing inorganic material particles and a resin material, A separator-integrated electrode, comprising: a second porous layer made only of a fiber made of a resin material. The average thickness of the second porous layer x, if the average thickness of the first porous layer and y, a, according to claim 1 wherein 0.5 ≦ x / (x + y ) ≦ 0.95 Separator integrated electrode.   The resin-made fibers forming the second porous layer are polypropylene, polyethylene, polystyrene, polyethylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene iso Phthalate, polyvinylidene fluoride, polytetrafluoroethylene, poly (vinylidene fluoride-tetrafluoroethylene) copolymer, poly (vinylidene fluoride-hexafluoropropylene) copolymer, poly (vinylidene fluoride-tetrafluoroethylene-hexa) Fluoropropylene) copolymer, poly (tetrafluoroethylene-hexafluoropropylene) copolymer, polyvinyl chloride, polyvinylidene chloride-acrylate copolymer, polyacryloni Ril, polyacrylonitrile-methacrylate copolymer, polycarbonate, polyarylate, polyester carbonate, polyamide, aramid, polyimide, polycaprolactone, polylactic acid, polyvinyl alcohol, polyglycolic acid, collagen, polyhydroxybutyric acid, polyvinyl acetate, polypeptide and The separator-integrated electrode according to claim 1 or 2, comprising at least one selected from a polymer material of these copolymers.   The inorganic material particles contained in the first porous layer are at least one selected from titania (excluding anatase structure), alumina, zirconia, and magnesia. The separator-integrated electrode as described. The separator-integrated electrode according to any one of claims 1 to 4, wherein the fiber of the resin material forming the second porous layer is formed by an electrospinning method. A non-aqueous electrolyte secondary battery comprising the separator-integrated electrode according to claim 1 and a counter electrode paired with the separator-integrated electrode, wherein the counter electrode is a current collector A counter electrode mixture layer formed on the surface of the separator, and the counter electrode mixture layer is disposed so as to be in contact with the second porous layer of the separator integrated electrode. A non-aqueous electrolyte secondary battery in which the first porous layer and the second porous layer are impregnated with a non-aqueous electrolyte.

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